diff --git a/cbits/cbits.c b/cbits/cbits.c
index cf7c85c..b1acc59 100644
--- a/cbits/cbits.c
+++ b/cbits/cbits.c
@@ -71,6 +71,9 @@ const static bool is_bigendian = false;
 /* test whether octet in UTF-8 steam is not a continuation byte, i.e. a leading byte */
 #define utf8_lead_p(octet) (((octet) & 0xc0) != 0x80)
 
+/* 0 <= x <= 0x110000 */
+typedef HsWord codepoint_t;
+
 /* Count number of code-points in well-formed utf8 string */
 size_t
 hs_text_short_length(const uint8_t buf[], const size_t n)
@@ -246,14 +249,14 @@ hs_text_short_decode_cp(const uint8_t buf[])
 }
 
 /* decode codepoint starting at buf[ofs] */
-uint32_t
+codepoint_t
 hs_text_short_ofs_cp(const uint8_t buf[], const size_t ofs)
 {
   return hs_text_short_decode_cp(buf+ofs);
 }
 
 /* reverse-decode codepoint starting at offset right after a code-point */
-uint32_t
+codepoint_t
 hs_text_short_ofs_cp_rev(const uint8_t *buf, const size_t ofs)
 {
   /*  7 bits | 0xxxxxxx
@@ -314,30 +317,30 @@ hs_text_short_ofs_cp_rev(const uint8_t *buf, const size_t ofs)
 
 /* Retrieve i-th code-point in (valid) UTF8 stream
  *
- * Returns 0xFFFFFFFF if out of bounds
+ * Returns -1 if out of bounds
  */
-uint32_t
+codepoint_t
 hs_text_short_index_cp(const uint8_t buf[], const size_t n, const size_t i)
 {
   const size_t ofs = hs_text_short_index_ofs(buf, n, i);
 
   if (ofs >= n)
-    return UINT32_C(0xffffffff);
+    return -1;
 
   return hs_text_short_decode_cp(&buf[ofs]);
 }
 
 /* Retrieve i-th code-point in (valid) UTF8 stream
  *
- * Returns 0xFFFFFFFF if out of bounds
+ * Returns -1 if out of bounds
  */
-uint32_t
+codepoint_t
 hs_text_short_index_cp_rev(const uint8_t buf[], const size_t n, const size_t i)
 {
   const size_t ofs = hs_text_short_index_ofs_rev(buf, n, i);
 
   if (ofs >= n)
-    return UINT32_C(0xffffffff);
+    return -1;
 
   return hs_text_short_decode_cp(&buf[ofs]);
 }
diff --git a/src/Data/Text/Short/Internal.hs b/src/Data/Text/Short/Internal.hs
index 6de15a5..b8852dc 100644
--- a/src/Data/Text/Short/Internal.hs
+++ b/src/Data/Text/Short/Internal.hs
@@ -699,9 +699,11 @@ encodeStringShort te = BSS.toShort . encodeString te
 isValidUtf8 :: ShortText -> Bool
 isValidUtf8 st = (==0) $ unsafeDupablePerformIO (c_text_short_is_valid_utf8 (toByteArray# st) (toCSize st))
 
+type CCodePoint = Word
+
 foreign import ccall unsafe "hs_text_short_is_valid_utf8" c_text_short_is_valid_utf8 :: ByteArray# -> CSize -> IO CInt
 
-foreign import ccall unsafe "hs_text_short_index_cp" c_text_short_index :: ByteArray# -> CSize -> CSize -> IO Word32
+foreign import ccall unsafe "hs_text_short_index_cp" c_text_short_index :: ByteArray# -> CSize -> CSize -> IO CCodePoint
 
 -- | \(\mathcal{O}(n)\) Lookup /i/-th code-point in 'ShortText'.
 --
@@ -719,8 +721,7 @@ indexMaybe st i
   | i < 0      = Nothing
   | otherwise  = cp2chSafe cp
   where
-    cp = CP $ fromIntegral $
-         unsafeDupablePerformIO (c_text_short_index (toByteArray# st) (toCSize st) (fromIntegral i))
+    cp = CP $ unsafeDupablePerformIO (c_text_short_index (toByteArray# st) (toCSize st) (fromIntegral i))
 
 -- | \(\mathcal{O}(n)\) Lookup /i/-th code-point from the end of 'ShortText'.
 --
@@ -738,10 +739,9 @@ indexEndMaybe st i
   | i < 0      = Nothing
   | otherwise  = cp2chSafe cp
   where
-    cp = CP $ fromIntegral $
-         unsafeDupablePerformIO (c_text_short_index_rev (toByteArray# st) (toCSize st) (fromIntegral i))
+    cp = CP $ unsafeDupablePerformIO (c_text_short_index_rev (toByteArray# st) (toCSize st) (fromIntegral i))
 
-foreign import ccall unsafe "hs_text_short_index_cp_rev" c_text_short_index_rev :: ByteArray# -> CSize -> CSize -> IO Word32
+foreign import ccall unsafe "hs_text_short_index_cp_rev" c_text_short_index_rev :: ByteArray# -> CSize -> CSize -> IO CCodePoint
 
 
 -- | \(\mathcal{O}(n)\) Split 'ShortText' into two halves.
@@ -1437,15 +1437,15 @@ writeRepChar mba ofs = do
 -- beware: UNSAFE!
 readCodePoint :: ShortText -> B -> CP
 readCodePoint st (csizeFromB -> ofs)
-  = CP $ fromIntegral $ unsafeDupablePerformIO (c_text_short_ofs_cp (toByteArray# st) ofs)
+  = CP $ unsafeDupablePerformIO (c_text_short_ofs_cp (toByteArray# st) ofs)
 
-foreign import ccall unsafe "hs_text_short_ofs_cp" c_text_short_ofs_cp :: ByteArray# -> CSize -> IO Word32
+foreign import ccall unsafe "hs_text_short_ofs_cp" c_text_short_ofs_cp :: ByteArray# -> CSize -> IO CCodePoint
 
 readCodePointRev :: ShortText -> B -> CP
 readCodePointRev st (csizeFromB -> ofs)
-  = CP $ fromIntegral $ unsafeDupablePerformIO (c_text_short_ofs_cp_rev (toByteArray# st) ofs)
+  = CP $ unsafeDupablePerformIO (c_text_short_ofs_cp_rev (toByteArray# st) ofs)
 
-foreign import ccall unsafe "hs_text_short_ofs_cp_rev" c_text_short_ofs_cp_rev :: ByteArray# -> CSize -> IO Word32
+foreign import ccall unsafe "hs_text_short_ofs_cp_rev" c_text_short_ofs_cp_rev :: ByteArray# -> CSize -> IO CCodePoint
 
 ----------------------------------------------------------------------------
 -- string & list literals